Large animals suffer from a variety of diseases or illnesses which vary in severity from life threatening to minor ailments. Even minor illnesses may result in consequences (e.g. weight loss) which may adversely affect the economic value of the animal. For example, some horses suffer from chronic obstructive pulmonary disease (see, e.g., F. J. Derksen et al., Airway Reactivity in Ponies with Recurrent Airway Obstruction (Heaves), Journal of Applied Physiology 58(2): 598-604 (1985)). Obstructive lung disease, like asthma, is characterized by acute episodes of airway obstruction due to constriction of airway muscles. The resulting bronchoconstrictive state can result in serious adverse health consequences for the horse due to clinically compromised breathing.
The art is replete with devices and methods for delivering medicaments, vaccines or therapeutic agents to large animals for treatment or cure of diseases or illnesses. Obstructive lung disease in horses has been treated by injecting relatively large doses of medication directly into the blood stream of the horse. Large doses (relative to an aerosol dose) of the medication are often required since the medication has not been specifically targeted to the lungs of the horse. Those larger doses increase the risk of undesirable side effects.
Delivering a medicament or therapeutic agent in aerosol form is becoming increasingly popular. For example, U.S. Pat. Nos. 3,915,165 and 4,143,658 describe intratracheal injection systems for injecting dry medicaments in a gaseous suspension into the trachea of an animal in order to treat pneumonia. That system includes a needle (e.g., a catheter) that is inserted into the lumen of the trachea of the animal by puncturing the wall of the trachea. The dry medicaments are then administered through the catheter. Also, a pirbuterol aerosol has been administered through a tube inserted into a chronic tracheostoma in a horse (see, F. J. Derksen et al., Aerosol Pirbuterol: Bronchodilator Activity and Side Effects in Ponies With Recurrent Airway Obstruction (Heaves), Equine Veterinary Journal, 24 (2), pages 107-112 (1992)).
U.S. Pat. No. 5,062,423 is directed to a method of end apparatus for delivering a dose of an aerosol medicament to the lungs of a large animal such as a horse. A distal end of an endotracheal-like nasal tube is inserted via a nostril of the horse into its nasal-pharyngeal cavity. The nasal tube prevents aerosolized medicaments from becoming entrained or adsorbed onto the tissue between the opening of the nostril and nasal-pharyngeal cavity of the horse. However, insertion of the nasal tube calls for the operator to place the distal end of the tube in the nasal-pharyngeal cavity of the horse. Such precise placement of the nasal tube may be a difficult task to perform repeatedly.